Technical Field
The present disclosure relates to a method for feeding electric energy into an electrical power supply network, which may also be a locally delimited stand-alone network, by means of a wind turbine. In addition, the present disclosure relates to a wind turbine for implementing such a method, and the present disclosure relates to a wind farm made up of multiple wind turbines.
Description of the Related Art
Wind turbines are known and are generally used to generate electric energy from wind and to feed it into an electrical power supply network. Unfavorable environmental conditions may be problematic for such methods or for wind turbines used to carry them out. One environmental condition is, for example, the prevailing wind. Wind turbines are generally adaptable to the particular wind conditions via their controllers, and wind turbines are also generally designed for specific wind classes, for example, locations having weak winds or locations having strong winds. If, by way of exception, the wind becomes so strong that it may pose a risk to the wind turbine, measures must be taken to protect the wind turbine. One such example of taking storms into account is described in the European patent EP 0 847 496. There, it has already been proposed to reduce the operation of the wind turbine as the wind increases further, in the event of wind which is too strong.
Methods are also known which deal with ice formation on rotor blades and, for example, propose heating a rotor blade for de-icing purposes, for example, the document EP 0 842 360.
However, completely different problems may occur if particularly wet or dry conditions or particularly warm or cold conditions occur. It is often advisable to design the wind turbine for these specific locations. For example, the wind turbine manufacturer ENERCON operates a wind turbine in the Antarctic which is subjected to conditions which are completely different, for example, from those of a wind turbine in Spain. Very low temperatures may affect totally different characteristics of the wind turbine. For example, the wind turbine may experience higher loads due to higher air density. This becomes noticeable in particular on the rotor blades, and may thus be observed indirectly or even directly on the tower. Higher notched impact strength of the cast materials may also be a result of particularly low temperatures. Low temperatures also affect the viscosity of the lubricants, which in particular become more viscous as a result, thus affecting the lubricity and possibly even inhibiting it in extreme cases. Even composite fiber materials may be affected by low temperatures and may, for example, become brittle.
Designing the specific materials for very low temperatures may be extremely costly and may also frequently result in a highly customized approach, for which empirical values are thus often non-existent or limited. In addition, although there are cold and hot locations, the temperatures at a single location are not always equally cold or hot. As is generally known, there are locations, in particular continental locations, having very high temperature fluctuations. These temperature fluctuations may occur in a distributed manner both over the course of the year and over the course of the day, or may become quite noticeable during the transition between day and night.
The German Patent and Trade Mark Office have researched the following related art in the priority application for the present application: DE 10 2011 003 974 A1, US 2013/0101413 A1 and EP 2 535 567A2.